Mugshot. If you want to craft the best gear in the game, or you want the trophies, use Swain's mugshot in every fight you can. I spent 20 - 30 hours grinding for rare materials after finishing the game, and you will too unless you start stealing these materials as you go through the game. This applies largely to the alchemy trophy where you must make 120 of the items (or close to that). Craft 91% of all that is available in the game.
Oh, also you may want to want to only have 1 powerful familiar and 2 for leveling and evolving on each character since you need to own or have owned 250 of the familiars in the game. That is another trophy which may require a huge grind. Any questions or other tips? I feel like we need to collectively lessen the pain of the end game in Ni No Kuni.